CORALS AND THEIR DIVERSITY IN THE OCEANS

The high diversity of coral reef fish communities includes a large within-habitat component wherein large numbers of species may co-occur in a very small space. It has recently been suggested by Sale (1977, 1978), that the mechanism of maintaining such great diversity may depend to a relatively large degree on stochastic processes, that is, on the chance arrival of propagules (larvae) at a particular site as well as the unpredictable production of habitable space, rather than on more deterministic factors such as habitat structure, or biological factors such as fine partitioning of food or space resources or specific predator-prey relationships.

The contemporary or sequential analysis of the faunas of these structures has shown a high degree of variability among replicates. How-ever, because these structures were of such small size and were capable of accommodating only a small frac-tion of the available species pool, and because the individuals on such small structures usually did not remain long enough to reach adult size it is likely that the unpredictable settlement of species and their relatively high turnover rate may be artifacts of the small scale of the habitats studied.

In the western Atlantic Ocean, where the available species pool is presumably much smaller, For example, Goldman and Talbot [1976] cite figures of 398 and 850 species of coral reef fishes on reefs of comparable size in the Florida Keys and at a comparable latitude in the Great Barrier Reef system, respectively. Smith (1973) found a high degree of similarity between replicate samples of small reefs, as did Molles (1978) working in the Gulf of California (also with a small regional species pool). Gladfelter and Gladfelter (1978) also working in the western Atlantic, but with large coral patch reefs, two to four orders of magnitude larger than those used by the aforementioned authors, found a high degree of similarity among fish assemblages, and the degree of similarity of these assemblages was correlated with structural similarities of the reefs.

Difficulties in making generalizations about which factors are important in determining the struc-ture of coral reef fish communities seem to result from the fact that previous authors have worked with such small structures that the extrapolation of their results to reefs in general may not be valid, and also that different authors have worked in different oceans with species pools of apparently different magnitudes.
Conclusion

The high diversity of coral reef fish communities is permitted by a variety of factors other than random recruitment of larvae alone; of these, habitat structure is the most evident. Furthermore, the same factors are operating in both oceans, although their proportional roles may differ.

Differences in within-habitat diversity between Atlantic and Pacific sites can be explained partly by the greater availability of resources (e.g., plankton or greater spatial heterogeneity) at the latter, but undoubtedly other factors, as yet not clarified, are operating.  For Additional Information About Corals Go to http://aquatic-source.com

References
Goldman and Talbot 1976, 1978
Sale 1977, 1978
Smith and Tyler 1972